1. The Field of the Invention
The present invention relates to vascular access systems and devices. In particular, the present invention relates to vascular access systems and devices, that permit access to the blood flow while avoiding repeated punctures into the blood vessel being accessed.
2. Present State of the Art
Procedures that require the repeated access to blood vessels include dialysis and the delivery of medicines for an extended period of time. The multiple punctures that such repeated access necessitates eventually render the blood vessel unsuitable for further effective injections. In addition, some external blood treatment methods rely on the extraction of blood from an artery and on the subsequent injection of the treated blood into a vein. The characteristics of the fluid flow in an artery are significantly different from the characteristics in the fluid flow in a vein. These fluid flow dissimilarities may lead to additional adverse effects that detrimentally affect the long term accessibility of the blood vessels that must be accessed for the external blood treatment to be effectively performed. For example, in an arterio-venous graft constructed as a vascular access for dialysis, the blood flow and blood pressure characteristic of the arterial circulation are so different from the blood flow and blood pressure in the vein into which the blood of the AV graft flows, that the vein usually develops hyperplasia and stenoses.
It is desirable to provide devices, systems and methods that permit multiple access to a blood vessel for the purpose of delivering medicines into the patient""s blood stream in such a way that the receiving blood vessel is not so severely damaged that it becomes unavailable after a few medicine administrations.
It is also desirable to provide devices, systems and methods that permit multiple access to a blood vessel for external blood treatment, such as hemodialysis, in such a way that the blood vessel being accessed does not become unavailable for successive dialysis operations.
Furthermore, it would be desirable to provide a device that is suitable for multiple vascular access for the purpose of long term medicine delivery into the patient""s blood flow and also for the purpose of effectively practicing hemodialysis for a long period of time.
The practical advantages of such devices and systems would be considerably enhanced if the device or system is lodged subcutaneously and is reliably attachable to a blood vessel by anastomosis techniques. In addition, such a vascular access device or system would have to be appropriately configured to allow for controlled and selected blood flow through the device or system and to allow for a controlled delivery of physiologically active agents, such as medicines. These goals should be accomplished while minimizing, or avoiding to the maximum extent possible, undesirable adverse effects such as vessel thrombosis, blood stagnation, the formation of undesirable turbulence, and the formation of blood clots.
The present invention focuses on objectives described hereinbelow for solving problems which are associated with repeated vascular access, and provides devices, systems and methods with advantageous features for solving such problems.
A blood vessel that is repeatedly accessed, and in particular repeatedly punctured, deteriorates to the point that vascular access becomes increasingly difficult and eventually impossible. When vascular access places the blood vessel under exceptional fluid dynamics conditions or subjects the vascular tissues to the deleterious side effects of certain medications, vascular deterioration can be seriously accelerated. An example of such exceptional fluid dynamics conditions is the blood volume and pressure that a vein is subjected to when it receives the arterial blood flow from an AV (arterio-venous) graft that has been created to provide vascular access for dialysis.
Although an occasional vascular access can be performed at any one among a plurality of generally available access sites, the availability of vascular access sites for the intravenous delivery of medicine for a long period of time or for dialysis can be seriously diminished because vascular access under such conditions has to be performed repeatedly. For example, hemodialysis typically requires from about 150 to about 200 vascular access operations per year for a period that typically ranges form about 2 years to about 5 years.
It is therefore desirable to provide vascular access devices and systems that can be repeatedly accessed, and in particular repeatedly punctured, while avoiding the deleterious effects on the blood vessel itself. These systems and devices should be biocompatible and in particular they should not significantly perturb the normal blood flow within the blood vessel that is to be accessed. In addition, these systems and devices should be made of readily available materials that can be clinically manipulated according to known techniques. It is also desirable to provide methods for repeatedly accessing blood vessels, and in particular for repeatedly accessing veins in the practice of vein-to-vein hemodialysis, so that vein accessibility is not diminished by the repeated vein access.
The general object of this invention is to provide vascular access systems and devices that facilitate repeated vascular access while reducing, or even eliminating, the deleterious effects that the vascular tissue would otherwise be subjected to. More specifically, it is an object of this invention to provide vascular access systems and devices that permit access to the blood stream while avoiding repeated punctures into the blood vessel being accessed.
It is another object of this invention to provide vascular access systems and devices that can be attached to a blood vessel by known anastomosis techniques.
It is another object of this invention to provide vascular access systems and devices that can be used for the intravenous long term delivery of medicines and also be used in dialysis.
It is a further object of this invention to provide methods for external treatment of blood such as hemodialysis methods, and in particular vein-to-vein hemodialysis methods, that enable the practice of hemodialysis between two blood vessels, such as two veins, while avoiding deleterious effects on these vessels. These deleterious effects would otherwise reduce blood vessel accessibility thus rendering the number of feasible hemodialysis operations unacceptably small.
These and other objects of this invention are preferably achieved by devices that come an occlusal balloon in fluid communication with a port device, and by systems that comprise an occlusal balloon in fluid communication with a port device to be used in conjunction with a graft vessel that in turn is configured to be anastomosed to a blood vessel.
The devices and systems of this invention preferably feature materials that are suitable for their subcutaneous disposition. This feature advantageously permits the placement of the vascular access systems and devices at a location that is not directly exposed to external pathogens.
The devices and systems of this invention preferably feature materials that can be repeatedly punctured and that are self-sealing. These features advantageously permit multiple injection to and extraction from the vascular access systems and devices of a variety of fluids such as blood samples, biocompatible solutions, medicines, and blood to be dialyzed or to be received from a dialysis apparatus.
The devices and systems of this invention preferably incorporate features that facilitate the exposure of the blood stream to desired physiologically effective (or bioactive) agents. This exposure is achieved by contact or by transport phenomena. In any case, these features advantageously permit, inter alia, the delivery into the blood stream of medications at desired and controlled dosages. Another advantage derived from these features is that the blood stream can be exposed to an agent that prevents the formation of blood clots.
In one embodiment, an occlusal balloon is positioned in a graft vessel and is in fluid communication with a port device. The occlusal balloon may be impermeable or it may have permeable portion such as an integral permeable region or a permeable membrane attached to its delivery end. In an another embodiment the occlusal balloon and the graft vessel are integral.
Selective and controlled exposure to a physiologically active agent, such as heparin, is in some preferred embodiments, provided by letting such agent migrate from the interior of an occlusal balloon into the blood in the vessel being accessed. This migration of a physiologically active agent is preferably realized by diffusion across a semipermeable region or membrane of adequately chosen porosity. In addition, preferred embodiments of the semipermeable region or membrane function according to the present invention by allowing the migration of an aqueous fluid from the blood stream in the vessel being accessed into the interior of an occlusal balloon. This migration of aqueous fluid is preferably realized by permeation across a semipermeable region or membrane of adequately chosen porosity. By migrating from the blood stream into the interior of an embodiment of an occlusal balloon, this aqueous fluid keeps the occlusal balloon in a distended configuration by osmosis, thus preventing the invasion of the anastomosed graft by blood from the accessed vessel.
The methods of this invention focus on repeated vascular access that is facilitated by preferably subcutaneous devices and systems which can be repeatedly punctured while preserving their physical integrity, biocompatibility and operability. These characteristics advantageously permit the practice of hemodialysis according to the methods of this invention for the extended periods of time that are typically needed by patients.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.